1. Field of the Invention
The invention relates to medical equipment, and namely to devices for surgical treatment of pathologic structures of extended superficial regions of tissues, and particularly to cryo-ultasonic surgical instruments.
The invention can be used in clinical and ambulatory practice for surgical treatment of pathologic structures of local superficial regions of tissues, particularly malignant tumors and precancerous states. Instruments of this type may be utilized e.g. in dermatology and cosmetic medicine.
2. Prior Art
The inventive cryo-ultrasonic surgical instrument is designed for combined influence of deep freezing and ultrasound on a selected region of a tissue, thereby ensuring a relatively low traumatism of the procedure alongside with a high efficiency of treatment, simplicity of equipment and accessibility for surgeons of average skills.
It should be noted that prior art processes of cryogenic and therapeutic ultrasonic influences on tissues, which are used separately, are of significantly lower efficiency than the above mentioned combined influence.
Even in a rather deep freezing down to temperatures close to the boiling point of liquid nitrogen, viable cells may remain within the zone of influence, thereby creating the danger of recidivation, and in the cryogenic surgery of malignant tumors the danger of metastatic spreading.
To accomplish destruction of biological tissues by means of ultrasound, a high-power ultrasonic radiation above the stability threshold of cells and noncellular structures is generally used, which may adversely effect the organism as a whole.
In addition, in this case the complete destruction of the elements of pathologic structures is not guaranteed, and respectively relapses and metastases are not eliminated.
Moreover, to accomplish ultrasonic destruction under the specified conditions, unique ultrasonic generators and transmitters are required, which are inaccessible for ordinary clinics.
At present, surgical instruments are available, whose operation is based on a combination of cryogenic and ultrasonic influence on tissues. However, these instruments do not ensure high intensity of destruction of pathologic structures of these tissues due to the absence of geometric congruency between the zones of effective influence of each of the above factors.
Known in the art is a cryo-ultrasonic surgical instrument comprising a working portion performing ultrasonic oscillations. This portion is placed inside a device intended for cooling down to cryogenic temperatures (USSR Author's Certificate No. 460,869).
Destruction of a pathologic structure of a tissue is achieved in this instrument due to a mechanical tearing of the tissue under the effect of vibration of a working portion tip (saw) of the instrument at an ultrasonic frequency and a large amplitude. Due to the cooling, the tissues which are soft in the natural state, are frozen, which fact makes it possible to destruct them by the specified method. The forms of heat and acoustic fields, ensured by this instrument, are absolutely different, and the zone of their joint influence on a tissue is insignificant. Besides, the parameters of ultrasonic oscillations, required for the saw to accomplish mechanical destruction of the tissue, do not provide for a desired effect even within the zone where the above fields are congruent.
Another prior art cryo-ultrasonic surgical instrument comprises a cryodestructor disposed within a common housing and coupled to the source of a coolant medium, and an ultrasonic transmitter connected to a generator of electrical ultrasonic oscillations. The ultrasonic transmitter is disposed within a bore provided in the cryodestructor (U.S. Pat. No. 3,911,924).
Ultrasonic irradiation of tissues, accomplished by this instrument, however, has as its aim location of the freezing zone rather than destruction of said tissues, for which purpose an ultrasonic signal is formed as short impulses, and therefore it is impossible to ensure the intensity and time of ultrasonic irradiation required for combined influence on the tissue, because of a high pulse duty factor and a narrow directional pattern of an irradiation diagram also conditioned by location.
At the same time, in exciting continuous oscillations of the ultrasonic transmitter with required parameters, the above specified instrument cannot be practically utilized to carry out cryo-ultrasonic destruction since with the above described arrangement of the transmitter only a small portion of the total zone to be destructed is irradiated by an ultrasonic beam.
For this reason the destruction of a tissue occurs mainly under the effect of cryogenic temperatures, and the efficiency of combined influence of the above two factors on the tissue turns out to be low, which results in slowing down the reparation of tissues within the zone of necrosis and prolonging the term of treatment.